There is a camp of people who want rust to very strongly force you to see and opt in to anything which has cost (e.g. inserting a memory barrier, which Arc's clone does) because they want it to be the perfect low level language, and there's a camp of people who want to make some things more implicit and ergonomic because they want rust to be a more versatile language. And there's a very strong desire from most of community not to bifurcate the language into different variants, and instead keep everything super consistent...

i like the idea of keeping the language super consistent in general (along with open source development / rfc process), it feels like this leads to a (sometimes? mostly?) good level of thinking harder about features